U.S. Pat. Nos. 4,569,443 and 5,215,250 address many of the problems associated with pouring spout structures for paperboard cartons. However, one problem unsolved by the cartons of the two patents is how to provide optimal barrier protection for the material contained in a carton with a pouring spout, while at the same time providing a pouring spout that is easy for a consumer to open.
Typically, cartons with pouring spouts for containing hygroscopic material or particulate materials requiring a degree of barrier protection are adapted to prevent the absorption of moisture or other contaminants by having, for example, films or other coatings applied to or integrated with the carton walls. Sifting or leakage from pouring spout containers can be a particular problem, because the spout structure generally includes aligned or overlaid seams, edges, cuts or perforated lines. Cuts that penetrate completely through the carton walls are a particular problem, especially if the contents are in direct contact with the cuts and the cuts provide a pathway directly to the exterior of the carton.
U.S. Pat. Nos. 4,732,315; 4,718,557; 3,346,165; and 2,819,832 are representative of attempts to solve the barrier protection and leakage problems. The latter patent discloses a leak-proof carton with superimposed inside and outside spout openings. However, when such double perforated flap structures are used, the material contained in the carton may still leak out and moisture may still easily penetrate the carton, particularly when perforations and throughcuts in separate layers are adjacent or superimposed along their length.
U.S. Pat. No. 4,909,395 discloses a carton having a double panel end closure with an opening flap in the outer panel providing access to a dispensing aperture in an inner panel. The opening structure includes a partially pre-cut bridge in an adhesive area for securing the outer opening flap to the inner panel, but again, aligned cuts or cuts that run from the carton exterior to the inner opening can provide a path for moisture entry.
It is well recognized that it is desirable to have an opening structure that can provide evidence of attempted or actual tampering. In this regard, U.S. Pat. No. 4,569,443 discloses a carton with a pouring spout and a removable access tab that provides a means for determining whether tampering has occurred. U.S. Pat. Nos. 3,395,848; 4,706,875 and 4,799,594 all disclose recloseable opening and dispensing structures for cartons in which perforations or other lines of weakness are used to form a portion of the structure to help provide evidence of tampering if they appear to have been torn.
Another problem in cartons with pouring spouts is that the spout or carton may be damaged or rendered useless by pulling the spout too far out while opening it or forcing it inwardly too far into the carton interior when reclosing it. This problem is partially addressed in U.S. Pat. No. 5,215,250, wherein a spout structure includes wings for forming the sides of the spout and for guiding the outward travel of the spout. Another portion of the spout acts as a stop to prevent the spout from being pushed inadvertently into the carton interior. However, as mentioned above, the disclosed spout does not adequately address the problem of barrier protection and resistance to leaking, nor does it include positive stop features for controlling the inward and outward movement of the spout.
Clearly, despite the improvements described in the above-cited patents, there is a need for a carton including a durable, integral dispensing spout structure for powdered or granular materials that prevents leakage and provides barrier protection for the contents, while at the same time providing tamper evidence and easy opening.